Archa133,
Happy birthday

I am glad you posted.
Going no contact is not easy. I get it. For me it ended up mostly unannounced, until my BPD mother decided to write... Then I answered stating I couldn't accept her invitation to "go back into the family fold." There was a backlash, her flipping the tables on me, blaming me, projections in a follow up letter. To which I simply answered that I was not who she described in her letters... And I reiterated that I was opened to meeting with her in the presence of a psychologist, a mediator of sorts, to discuss our relationship.
But I remember feeling what you are describing now... Like I had to somehow anonce my NC to her, or explain her why.. I don't know, being in unannounced no contact left me with an unnerving feeling of still being attached to her and her emotional roller coaster, when I just wanted out of it. Like I was trapped in limbo, between two realities, and I was simply not seeing a road out of it.
I wrote a long letter that I couldn't muster the courage to send... And she ended up writing me first... Which forced me to anonce No Contact...
All this to say : I get your feeling. And I wish I could tell you what way is better : sending a letter or not... But in the end : you are the one leading the no contact, so it has to be on your own terms.
One thing I learned though, and regretted was that I blocked her on social media, when unfriending her would have been a more gentle approach... This is basically how I anonced No Contact, in a way... by unfriending her on Facebook and blocking her on messenger... not my proudest moment, but the only thing I had enough courage for... I ended up unblocking her a few weeks later when I realized that I was sending a message that I was angry, that I wanted to erase her and hurt her, which was not at all my goal. I did clarify this in my reply letter to her... We were already very low contact when I did that.
So I guess my road toward no contact was very awkward and clumsy... But I made it. And you will too. It helps not to see it as a complete no contact with double barricades...in the end : I did give her the key, which was a family meeting with a therapist. So really, our current no contact situation is her decision, because she is the one deciding not to meet me with a therapist...
I guess the question is : are you more comfortable with the idea of low contact, or do you need no contact to heal and find yourself?